共查询到20条相似文献,搜索用时 15 毫秒
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Adaptive transmission mode selection scheme for distributed wireless communication systems 总被引:2,自引:0,他引:2
《Communications Letters, IEEE》2006,10(7):573-575
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Satellite systems for personal communication networks 总被引:1,自引:0,他引:1
The paper addresses some issues related to Satellite Personal Communication Networks (S‐PCNs). The role of satellite communications
in that scenario is discussed, and some characteristics of S‐PCNs are identified. In addition, the problem of the integration
of S‐PCNs with the Universal Mobile Telecommunication System (UMTS) is considered. In this respect an original methodology
for accomplishing such integration is proposed; such methodology aims at avoiding complex protocol conversions at the interfaces
between the terrestrial and the satellite segment. The paper is partly based upon the work performed by the authors in the
framework of the European Community INSURED Project “INtegrated Satellite UMTS Real Environment Demonstrator”.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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A new scheme for minimising handover failure probability in mobile cellular communication systems, by exchanging channels between two mobiles moving in opposite directions across the endeavour area of adjacent cells is presented. The performance evaluation of the new scheme is carried out by computer simulation of a two cell model 相似文献
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A central problem in personal communication systems is to optimize bandwidth usage, while providing Quality of Service (QoS) guarantees to mobile users. Network mobility management, and in particular, location management, consumes a significant portion of bandwidth, which is a necessary overhead for supporting mobile users. We focus our efforts on minimizing this overhead. Unlike previous works, we concentrate on optimizing existing schemes, and so the algorithms we present are easily incorporated into current networks. We present the first polynomial time approximation algorithms for minimum bandwidth location management. In planar graphs, our algorithm provably generates a solution that uses no more than a constant factor more bandwidth than the optimal solution. In general graphs, our algorithm provably generates a solution that uses just a factor O (log n) more bandwidth than optimal where n is the number of base stations in the network. We show that, in practice, our algorithm produces near-optimal results and outperforms other schemes that are described in the literature. For the important case of the line graph, we present a polynomial-time optimal algorithm. Finally, we illustrate that our algorithm can also be used for optimizing the handoff mechanism. 相似文献
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提出了一种采集与传输数字图像/话音的方法,介绍了其总体方案以及设计重点,包括乒乓存储结构的改进、数据复接和控制逻辑的实现等。 相似文献
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文章提出了一种基于密集波分复用器(DWDM)和光分插复用器(OADM)、以物理拓扑为总线型、逻辑拓扑为星形的适合于铁路通信各站光接入的光传输网方案,描述了光节点结构及这种网络的波长重复利用和自愈保护功能,实验测试了逻辑单星形光网络的传输特性,分析了网络规模的限制因素. 相似文献
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Issues in satellite personal communication systems 总被引:2,自引:0,他引:2
In the paper various issues in personal satellite communications are addressed. Basic geostationary and non‐geostationary
satellite constellations are considered. The narrowband and wideband characterization of the mobile satellite channel and
related system implications are discussed. Satellite diversity is presented as a measure to overcome signal shadowing. The
capacity of TDMA and CDMA multiple access is estimated, taking into account co‐channel interference. Various network issues,
such as mobility management, radio resource management, call control, routing, and network integration are addressed. Finally,
some regulatory and political issues are mentioned which may be most relevant for market development and financial success
of satellite personal communication systems.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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The market demand for wireless communications has been demonstrated by the rapid growth of different second-generation wireless technologies that are optimized for particular applications and environments. Obvious examples include: digital cellular systems like GSM, ADC, PDC,and DCS1800 for widespread vehicular and pedestrian services, and cordless telecommunication systems based on CT2, DECT, and PHS standards for residential, business, and public cordless access applications. Efforts are also underway to consolidate the various radio environments and applications under a single standard for third generation wireless, i.e., FPLMTS. In the area of personal mobility, with the recent availability of “personal” numbers in various countries (e.g., 500 numbers in the United States), many fixed network operators are starting to offer such personal mobility services as “personal number service” and “number portability”. These services represent initial stages of full personal mobility that will be provided by UPT in both wireline as well as wireless environments. The expected heavy demand for PCS in the United States and the underlying market/regulatory forces are driving the standardization and business activity. A number of air interface standards for the 1900 MHZ PCS band are being considered, which are based on TDMA, CDMA, and FDMA technologies singly or in combination. Many are variations of existing digital cellular and cordless telecommunications technologies. PCS networking standards are also being developed; both for standalone systems and for systems that will utilize public switched network capabilities 相似文献
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An equicorrelation-based multiuser communication (ECBMC) scheme for direct-sequence code-division multiple-access (DS-CDMA) systems is presented. The ECBMC receiver has low computational complexity that is comparable to that of the conventional detector. By using the equality of cross correlations, the ECBMC scheme can completely eliminate multiple-access interference (MAI) in a synchronous single-path DS-CDMA network. The system performance is independent of the number of active users. The scheme is extended to include the effects of multipath fading. It is able to suppress a major portion of the MAI. This proposed ECBMC scheme is quite attractive for an MAI-dominant environment. 相似文献
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A new modulation scheme for IR-UWB communication systems 总被引:1,自引:0,他引:1
Since the poor performance of orthogonal binary Pulse Position Modulation (PPM) compared with binary Pulse Amplitude Modulation (PAM), this paper presents a new modulation scheme named Pulse Width Modulation (PWM) for Impulse Radio Ultra-WideBand (IR-UWB) communication systems. This modulation scheme uses pulses with equal amplitude and different widths to carry different information. The receiver employs differences between similarity coefficients among these pulses to distinguish different information. Bo... 相似文献
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A spectrally efficient scheme is described, for SCPC (single channel per carrier) communication systems, in which slightly modified MSK (minimum shift keyed) channels can be allowed to overlap spectrally, with a channel spacing equal to half the individual channel bit rate, without causing any crosschannel interference 相似文献
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Generalized correlation-delay-shift-keying scheme for noncoherent chaos-based communication systems 总被引:1,自引:0,他引:1
Tam W.M. Lau F.C.M. Tse C.K. 《IEEE transactions on circuits and systems. I, Regular papers》2006,53(3):712-721
In this paper, we propose a generalized correlation-delay-shift-keying (GCDSK) scheme for noncoherent chaos-based communications. In the proposed scheme, several delayed versions of a chaotic signal are first produced. Some of them will be modulated by the binary data to be transmitted. The delayed signals will then be added to the original chaotic signal and transmitted. At the receiver, a simple correlator-type detector is employed to decode the binary symbols. The approximate bit error rate (BER) of the GCDSK scheme is derived analytically based on Gaussian approximation. Simulations are performed and compared with the noncoherent correlation-delay-shift-keying (CDSK) and differential chaos-shift-keying (DCSK) modulation schemes. The effects of the spreading factor, length of delay, and the number of delay units on the BER are fully studied. It is found that GCDSK can achieve better BER performance than DCSK under reasonable bit-energy-to-noise-power-spectral-density ratios. 相似文献
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Eldek A.A. Elsherbeni A.Z. Smith C.E. Kai-Fong Lee 《Antennas and Propagation Magazine, IEEE》2002,44(5):146-155
Antenna designs are achieved for wideband operation by the use of a coplanar patch-slot antenna, fed by a coplanar waveguide. This design is easily tuned to operate at 2.45 and 5.75 GHz, with wide bandwidth for wireless systems. The operating frequency is controlled by modifying the patch dimensions. The return loss, input impedance, radiation pattern, directivity, gain, and efficiency of the proposed designs are computed and presented. A parametric study of the antenna is also introduced. 相似文献
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《Vehicular Technology, IEEE Transactions on》2005,54(6):1923-1931
A new three-dimensional (3-D) cellular system is proposed for air/ground (A/G) personal communications. The proposed system extends the Global System for Mobile Communication (GSM) to enable its subscribers to send and receive calls while traveling in the air using the same subscriber identity module (SIM)-the same mobile number-that is used for the ground network. Modifications to the GSM system architecture to develop the A/G system architecture are outlined. A multilayer service volume is proposed in which the coverage volume is divided into three coaxial cylindrical layers (cells) with each layer serving a limited part of the airspace. Capacity of the new proposed system based on the standard GSM concept is analyzed and compared to other alternative systems: Code Division Multiple Access (CDMA) and Frequency Division Multiple Access (FDMA). 相似文献
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Location update optimization in personal communication systems 总被引:1,自引:0,他引:1
Mobility tracking is concerned with finding a mobile subscriber (MS) within the area serviced by the wireless network. The
two basic operations for tracking an MS, location updating and paging, constitute additional load on the wireless network.
The total cost of updating and paging can be minimized by optimally dividing the service area into location registration (LR)
areas. There are various factors affecting this cost, including the mobility and call patterns of the individual MS, the shape,
size and orientation of the LR area, and the method of searching for the MS within the LR area. Based on various mobility
patterns of users and network architecture, the design of the LR area is formulated as a combinatorial optimization problem.
The objective is to minimize the location update cost subject to a constraint on the size of the LR area.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献